1. Field of the Invention
The present invention relates to a composite writing tool accommodating a plurality of writing shafts and selectively protruding one or another of these writing shafts to make it usable for writing, and more particularly to a composite writing tool provided with a knocking member protruding from its rear shaft for use in knocking.
2. Description of the Related Art
A conventional writing tool of this kind is disclosed, for instance, in Japanese Patent Laid-Open No. 2001-328393 whose application was filed by the same assignee as this application.
The composite writing tool described in the above Patent publication comprises a front shaft, a rear shaft, and an intermediate shaft inserted between the front shaft and the rear shaft. The intermediate shaft is separably coupled to the front shaft, but is rotatably coupled to the rear shaft so as to be unmovable in the axial direction of the rear shaft. The intermediate shaft combines the front shaft and the rear shaft in a separatable manner and in a combining state, allows them to rotate relative to each other and does not allow them to move relative to each other in the axial direction. The front shaft accommodates a plurality of writing shafts always urged in a backward direction, and guided by the intermediate shaft so as to be move in an axial direction. The composite writing tool further comprises a cam sleeve for holding one of the writing shafts in a protruding state, one of the writing shafts being selected upon a relative rotation between the cam sleeve and the front shaft and the intermediate shaft and guided in the axial direction by the intermediate shaft. The cam sleeve is disposed within the rear shaft so as to be unrotatable relative to the rear shaft but movable in the axial direction. The composite writing tool further comprises a knocking member coupled to the cam sleeve and protruding from the rear end of the rear shaft, whereby the writing shaft held to be protruded by the cam sleeve is subjected to the knocking operation when the knocking member is knocked.
The intermediate shaft has a rear sleeve portion which extends substantially concentrically into the rear shaft in order to couple the intermediate shaft to the rear shaft so as to be rotatable but unmovable in the axial direction of the rear shaft. The rear sleeve portion is provided with engaging protrusions at the rear end, and the engaging protrusions are engaged with an engaging step portion formed on the inner surface of the rear shaft.
Thus, this conventional configuration has a triple-sleeve structure consisting of the rear shaft, the intermediate shaft and the cam sleeve, and for this reason involves a problem that an outside diameter of the shaft tends to become greater. However, as it is necessary to arrange the cam sleeve and the intermediate shaft within the rear shaft and to link the cam sleeve to the knocking member, it is not easy to attach the intermediate shaft to the rear shaft with avoiding bulkiness.